The rate of fluid transport across rabbit corneal endothelium will be determined with an automatic technique. That rate will be correlated with the electrical properties of the endothelium. Measurements of rate of fluid movement, electrical potential difference, resistance and impedance will be carried out simultaneously in the same preparation. In other experiments, the transendothelial electrical properties and the rate of fluid transport will be correlated with the intracellular potentials of the endothelial cells. The results will be interpreted in terms of an existing model for water and electrolyte transfer across the endothelial layer.